Unfortunately it's kind of hard to play to the Summoner's hardwired jump jets, which provide substantial lift for a heavy mech, because of the low-slung arms. However the loyalty Summoner release will present a revolution in the Summoner chassis if the omnipods get released (I've noticed that the omnipods for the loyalty Executioner are available in the warehouse even though the EXE-C is not actually available in the store, will it be the same story here?). This is due to the fact that the new Summoner omnipods will have an energy point in the right side torso, allowing for more effective PPC fire—no matter where the new hardpoint is mounted, it will pretty much certainly be higher than the current arm mount. So not only can you put your peep on the same level as your Gauss rifle, but alternatively you could just have 5 energy points instead of 4. Or 6 missile points instead of 5 since one of the new ST pods includes an additional missile point (AND an energy point, wow what a deal!).
Anyway, speculation about the future aside, right now you have to play to its forward and lateral maneuverability more than its vertical. The Summoner has some of the best quirks on a Clan mech (proof enough that it sucks as a chassis). Some structure bonus, good maneuver if you choose the right CT. And that sweet, sweet +5% speed quirk on all variants. So hit and run weapons are what's in. SRMs, ER PPCs, and, my personal favorite, the LB20x autocannon (not the ultra autocannon 20 because pellet stream? Screw that). The Summoner does of course offer a left arm with glorious LBx fire rate and spread quirks which I think give it the best LBx performance of any clan mech (not completely sure on that so don't quote me).
Now the Summoner DOES have high mount ballistics, and the right side torso is especially useful because the gun is right under your face. Perfect for the Gauss rifle. Which is why the most meta build for the Summoner involves a face-mounted Gauss rifle and a PPC in the right arm. UAC5s could also be good (read: decent enough to be playable) but I haven't gotten a chance to try it yet. One thing I wouldn't do, ironically, is take LRMs. Summoner LRM performance just leaves something to be desired. It's just not really worth the tonnage with that (extremely) limited pod space, what with Clan LRMs paling in comparison to their IS counterparts.
My personal favorite build is ER PPC in the right arm and LB20 in the left. I dish out major amounts of damage with it, and even though you're kind of at risk of Swiss Army Knifing it, it does mean you're useful in every phase of the battle and have good heat management to boot. And did I mention the LBx quirks. (Addendum: ER PPC quirks are pretty awesome too, I especially love the velocity.)
Edited by Arianrhod, 19 August 2016 - 12:13 AM.